VOID RATIO EVOLUTION INSIDE SHEAR BANDS IN TRIAXIAL SAND SPECIMENS STUDIED BY COMPUTED-TOMOGRAPHY

A study of strain localization in triaxial tests on sand, using comput ed tomography is reported, The inception and the development of the lo calization are detected and described, both qualitatively and quantita tively, The complex geometrical structures involved in the localizatio n patterns are described and the local void ratio evolution in the loc alization zone(s) is determined, Dense and loose Hostun RF sand specim ens were tested under a confining pressure of 60 kPa, It is shown that strain localization can occur in different localization patterns depe nding on test conditions; a mechanism involving, simultaneously, a cen tral cone and a set of planes in pairs was found for many of the speci mens tested, The comparison of the local void ratio evolution in the s hear zones with the global void ratio measurement supports the importa nt conclusion that a limit void ratio is reached in the shear zones, T his ratio is significantly different from the final void ratio defined from the global measurements; the lack of physical relevance of the l atter is established.